Electric wheelchairs are commonly fitted with a tilt arrangement which allows adjustment of the orientation and/or the height of the wheelchair seat. Such adjustment may be anterior, i.e. forward, posterior, i.e. backwards, tilting and/or lifting of the seat. A seat occupant or caretaker may thereby for example set the seat position according to desire or current need of the occupant. Moreover, adjustment of the seat orientation may be a desirable feature for control purposes to stabilise the wheelchair depending on speed and travel on inclined surfaces.
EP1997466 discloses a wheelchair which provides posterior tilt, anterior tilt, full standing anterior tilt and lift. For this purpose, the wheelchair comprises a plurality of interacting actuators and levers. A first actuator is arranged to actuate a pivotable lever which is provided with a second actuator. Interaction between the first actuator and the pivotable lever provides posterior tilt, and further interaction with the second actuator enables lift and anterior tilt.
CH697181 A5 discloses a seating unit for use in wheel chairs. The seating unit sits on a carriage frame and is built as a separate unit from the frame. The seating unit comprises a seating surface, a back support and leg supports on an upright frame and can be adjusted via a first aggregate or manually adjustable upright mechanism for lifting the upright frame in a standing position or lowering it to a seating position.
One problem with existing solutions is that upon tilting, especially posterior tilt, the centre of gravity of an occupant is maintained which may render transportation with the wheelchair unstable, subjecting the wheelchair and its occupant to the risk of tipping over.